The invention relates to apparatus and methods for interfacing between automatic wafer probe machines, automatic integrated circuit testers, and probe cards which support needles that make electrical contact with bonding pads of integrated circuits on wafers, and more particularly to improvements that allow inexpensive, rapid, convenient upgrading of an entire wafer probe test system without complete redesign of the interface apparatus.
Each semiconductor wafer may include hundreds of integrated circuit die (i.e., chips), and it is necessary to "probe test" each die before the wafer is cut into the individual integrated circuit die which then are packaged. Such testing requires the bonding pads of each chip to be electrically connected to an automatic tester. In a typical probe test system, a "test head" supports an "interface assembly". The interface assembly supports a "probe card". The probe card supports all of probe needles required to probe test a particular semiconductor die. The tips of the probe needles must provide electrical contact with corresponding bonding pads of the die under test (DUT). The shank of a probe needle is typically 5 to 10 mils in diameter, and the wafer to be probed is supported on a wafer chuck of a "wafer probe machine" that automatically handles wafers. The chuck provides indexed translation in the x and y directions to bring the individual chip bonding pads into alignment with the pins of a probe card and is moveable in the z direction to press the chip bonding pads against the contact tips of the probe needles. After alignment of the probe needles with the corresponding bonding pads of the integrated circuit die has been accomplished, the wafer chuck is raised through an appropriate distance to cause the probe tips to contact the bonding pads of the chip to be tested next. The die testing often needs to be performed at high speed or high frequency, for example at a 200 MHz data rate, or even much higher.
Typically, a semiconductor integrated circuit wafer fabrication facility purchases a state-of-the-art wafer probe machine. The integrated circuit fabrication facility also buys a state-of-the-art electronic "automatic IC test system" which executes computer programs to (1) generate the necessary operating stimulus signals that need to be applied to the DUT to cause it to operate, and (2) measure the response signals produced by the integrated circuit in response to the stimulus signals. The probe card applies the stimulus signals via some of the test needles and measures response signals on those and/or other needles in order to test the DUT.
Thus, the "interface system" constitutes the mechanical fixturing supported by the wafer probe machine to (1) hold the probe card and (2) provide the electrical signal paths between the probe card and the automatic IC test system.
The closest prior art is believed to be the assignee's own prior interface systems, which have included (1) a "base system" in which a probe card is supported in a probe card tray, and (2) an insert ring which includes suitable camming surfaces that receive corresponding cam elements attached to a "POGO tower" to compress its lower spring-loaded POGO pin contacts against corresponding conductive pads on the upper surface of the probe card. Such POGO towers (which include so-called "direct docking" POGO towers and "cable" POGO towers) include an annular ring carrying double ended, spring-loaded, electrically conductive POGO pins that extend downward from the bottom surface of the POGO tower to the conductive pads of the probe card. (In a direct docking POGO tower, the upper ends of the POGO pins contact conductive pads of a PIB ("performance interface board") which provides electrical paths to a test head of the electronic test system. In a cable type POGO tower, the upper ends of the POGO pins directly contact corresponding conductors of a cable system connected to the electronic test system.)
Referring to FIG. 1, which discloses a portion of the above mentioned prior art thought to be most relevant to the present invention, interface system 1 includes an insert ring 3 suitably attached to a support surface 2A of an automatic probe machine 2. Insert ring 3 includes a cylindrical opening in which a rotatable lock ring assembly 15 includes three cam slots each having a sloped upper cam surface 7. Lock ring assembly 15 is rigidly connected to handle 4. The upper cam surfaces 7 serve as sloped ramps that can be followed downward as lock ring assembly rotates in the direction of arrow 12 by three subsequently described corresponding cam followers 23 that are rigidly attached to the outer cylindrical wall of a POGO tower 10. POGO tower 10 is coupled by multiple conductors 13 to an automatic electronic IC test system 14.
POGO tower 10 is supported by a lid 11 which is attached by a hinge assembly 18 to insert ring 3. A probe card tray 5 is rigidly attached to the bottom of insert ring 3, and supports a probe card 6 having conductive pads to be contacted by spring-loaded lower POGO pin contacts (not shown) extending from the bottom surface of POGO tower 10. After lid 11 and POGO tower 10 have been lowered so that cam followers 23 are located in the open ends of the cam slots and the POGO pin contacts are about 0.1 inches above the corresponding conductive pads on the probe card 6, handle 4 is rotated in the direction of arrow 12 so that the upper cam surfaces 7 cause cam followers 23 and hence POGO tower 10 to be pulled a predetermined distance downward to press the spring-loaded POGO pin lower contacts against the corresponding conductive pads on probe card 6.
Cam blocks 18 are attached to the upper surface of insert ring 3. Cam blocks 18 each support a cam follower 18A at a suitable angle so cam followers 18A roll on sloped arcuate surfaces 16 on the upper outer edge of lock ring assembly 15. Cam followers 18A counter the upward force produced on lock ring assembly 15 by the compressed POGO pins.
The main problems of the closest prior art interface systems occur because nearly every interface system is different. It should be understood that various users of wafer probe/test systems make very large investments to purchase a wide variety of different commercially available IC electronic test systems, automatic wafer probe machines, POGO towers, and/or probe cards. Consequently, nearly every complete wafer probe/test system is "built to order". Therefore, an entire new interface system ordinarily must be designed every time a user purchases an up-to-date electronic IC test system, automatic probe machine, probe card, and/or associated POGO tower. Such "building to order" of an interface system requires a considerable amount of time because it is impractical for a business concern providing interface systems to attempt to maintain an inventory of all of the components of a large number of slightly different "standard" interface systems.